1. Field of the Invention
The present invention relates to building insulation, which includes a blanket of mineral fibers, and a facing sheet adhered to the top of the blanket to form a batty for use in insulating metal building walls and ceilings.
2. Brief Description of the Prior Art
Insulation blankets formed from mineral fibers, very often fiber glass, are well known and have long been used for building insulation. The thickness of the mineral fiber blanket is generally proportional to the insulative effectiveness or xe2x80x9cR-valuexe2x80x9d of the insulation. The blanket is typically formed from glass fibers, often bound together using a resinous material. The insulation may be compressed after manufacture and packaged, so as to minimize the volume of the product during storage and shipping and to make handling and installing the insulation easier. After the packaging is removed, the insulation batty tends to quickly xe2x80x9cfluff upxe2x80x9d to its prescribed label thickness for installation.
Such insulation typically has exposed mineral fiber surfaces on two sides and on the one or both of the major surfaces of the blanket. The exposed surfaces permit air to be easily removed from the insulation batty during compression prior to packaging, and to quickly reenter the product after the packaging is removed at the installation site. However, the exposed surfaces can make installation troublesome, as contact may irritate exposed flesh, and some release of unbound fibers and dust into the working environment may occur. Similarly, it is desirable to avoid installation in such a way so that exposed surfaces are presented for subsequent contact. Circumstances may sometimes dictate that insulation without an attached vapor retarder, such as unfaced batts, is used. For example, when additional insulation is being added over previously installed material having a vapor retarder, it is desirable to avoid providing yet another vapor retarder. In these cases, however, the additional unfaced insulation batts are hidden from the building""s interior by preexisting walls, ceiling panels, etc.
Buildings having walls and roofs formed using metal panels frequently offer an optimum balance of cost and performance for industrial and commercial uses. To provide both thermal and acoustic insulation such buildings are often insulated using fiber glass insulation batts. This metal building insulation is typically faced with vapor barrier sheet material as a vapor retarder, and the insulation is installed with the retarder towards the conditioned spaces within the building. The insulation is normally applied over or in between the structural members of the building and is held in place by the covering sheets or by an insulation support system.
Metal building roof assemblies typically include a series of purlins arranged over and perpendicular to the structural rafters. Insulation batts are secured in between or over the purlins and are covered by the roof decking. A variety of systems have been developed for installing insulation in existing and new metal buildings, such as disclosed for example, in U.S. Pat. Nos. 4,375,742, 5,442,890, 5,692,352 and 5,724,780.
Depending on the activities performed in the building, metal buildings for industrial and commercial uses can present noisy environments for their occupants. For example, manufacturing and even warehousing operations can generate significant levels of noise. Hard metal interior surfaces simply reflect and exacerbate such noise. Covering metal interior surfaces with fiber glass insulation can help ameliorate this situation through sound absorption. For example, a fiber glass batty covered with a vapor retarder and having a nominal thickness of 3xe2x85x9 inches can have a sound absorption coefficient of 0.52 at 125 Hertz and 0.45 at 2000 Hertz (ASTM C 423-Type A mounting), while an unfaced batty with a nominal thickness of 3xc2xd inches can have a sound absorption coefficient of 0.38 at 125 Hertz and 0.97 at 2000 Hertz. Although some reduction in noise is achieved with the faced insulation, this level of sound absorption remains below that achievable with unfaced insulation, and an additional reduction in noise is desirable.
The vapor retarder serves two important purposes in the typical metal building insulation installation. First, it serves to retard the transmission of moisture-laden interior air to the cold interior surface of the metal walls and/or roof of the building during the winter, thus avoiding or reducing condensation related problems. Second, it protects the fiber glass insulation from contact and abuse, especially when metal building are constructed without rigid interior walls and ceilings, so that the insulation is presented directly to the interior.
As noted above, occasionally it is desirable to employ insulation batts without an integral vapor retarder facing. For example, it may be desirable to insulate interior walls for acoustic reasons. Similarly, it may be desirable to increase the effective xe2x80x9cR-valuexe2x80x9d of previously installed insulation in exterior walls or roofs to decrease heat or air-conditioning loses due to an increase in fuel costs or to Increase acoustic insulation because different, noisier activities are being conducted in the building. If the preexisting insulation already includes a vapor retarder, installing insulation with another vapor retarder should be avoided so that moisture is not trapped between the two vapor retarders. On the other hand, it is desirable to protect the interior face of the additional insulation from abuse. However, providing a rigid interior wall or ceiling surface over the new insulation is likely to prove prohibitively expensive and may not improve sound absorption.
There is a need for insulation for metal building, which does not include a vapor retarder, facing but which provides protection against abuse after installation and provides sound absorption. Also, if a vapor barrier is required, an insulation system that provides good sound absorption plus a vapor barrier is needed.
The present invention provides a solution to the problems associated with the installation of mineral fiber blankets having unfinished surfaces for use as insulation in metal buildings. In addition, the present invention provides metal building insulation with enhanced sound absorption and noise reduction properties.
The present invention provides a mineral fiber insulation assembly for use in insulating metal building walls and ceilings. The insulation assembly includes a first insulation layer comprising glass fiber, preferably, a low density glass fiber material, with a density of from about 0.3 to 1.5 pounds per cubic foot (4.8xc3x9710xe2x88x923 g/cm3 to 2.4xc3x9710xe2x88x922 g/cm3). The first insulation layer preferably takes the form of a glass fiber insulation batty having a first major face, a second major face, and a pair of opposed side faces. Preferably, the first major face is covered with a vapor retarder material, which is preferably bonded to the face using a suitable adhesive material. The insulation assembly also includes a second insulation layer comprising glass fiber. This second layer also preferably comprises a low-density glass fiber material. The second insulation layer also preferably takes the form of a glass fiber insulation batty having a first major face and a second major face. The first major face of the second insulation layer has a covering of porous material, preferably a perforated film formed from a plastic material such as vinyl, for example, a vinyl film having a thickness of from about 2 to 3 mils. The perforations preferably are uniformly distributed over the film, and comprise at least about 20 percent of the surface of the film. Alternatively, a nonwoven fabric facing can be used. The nonwoven fabric facing is preferably selected from rayon, spun-bonded polyester, spun-bonded polyolefin, and thermally bonded polypropylene. The second major face of the second insulation material is provided adjacent to the covering of vapor retarder material on the first major face of the first insulation layer.
In another embodiment the present invention provides a composite structure comprising a metal building panel, such as an exterior wall or roof deck panel, and an insulation assembly as described above.
In a third embodiment, the present invention provides a composite structure including a metal building panel, and an insulation assembly comprising single layer of glass fiber. The glass fiber layer preferably comprises a low density glass insulation batty having a first major face with a covering of porous material adhered thereto.